Seconding this: PureData is very good - used it throughout my second and third years of university to create soundscapes and scores. A little DSP knowledge is required to get really good, but very rewarding once you get the hang of it.

Designing Sound by Andy Farnell is a great book to learn about ~PD and sound design in general: https://www.amazon.co.uk/Designing-Sound-Press-Andy-Farnell/...